This invention relates to thermonuclear fuel targets, particularly to small thermonuclear fuel targets, and more particularly to such targets for a laser fusion reactor which includes material for producing an atmosphere around the target.
Laser-induced fusion has recently joined magnetic-confinement fusion as a prime prospect for generating controlled thermonuclear power. During the past few years much effort has been directed toward the development of fusion fuel targets or capsules and laser-initiated systems for causing implosion and thermonuclear burn of such capsules as exemplified by U.S. Pat. Nos. 3,489,645 issued Jan. 13, 1970 to J. W. Daiber et al; 3,624,239 issued Nov. 30, 1971 to A. P. Fraas; 3,723,246 issued Mar. 27, 1973 to M. J. Lubin; 3,723,703 issued Mar. 27, 1973 to K. W. Ehlers et al; and 3,762,992 issued Oct. 2, 1973 to J. C. Hedstrom. Compression of fuel capsules by laser to initiate thermonuclear fusion is described in detail, for example, by an article published in Nature, Vol. 239, No. 5368, pp. 139-142, Sept. 5, 1972 entitled "Laser Compression of Matter to Super-High Densities: Thermonuclear (CTR) Applications" by John H. Nuckolls et al, and an article published in Physics Today, August 1973 entitled "Laser-Induced Thermonuclear Fusion" by John H. Nuckolls et al. By way of example, copending U.S. patent application Ser. No. 306,237 filed Nov. 14, 1972, now abandoned in the name of L. L. Wood et al discloses and claims a system for generating electricity by implosion of laser-fusion targets.
Also, recent efforts have been directed to the fabrication of laser-fusion targets or fuel capsules compatible with laser energy and cost requirements for commercial power production as described briefly in the above-cited Nature article and in greater detail in an article entitled "Spherical Hydrogen Targets for Laser-Produced Fusion" by I. Lewkowicz, J. Phys. D: Appl. Phys., Vol. 7, 1974. Also, copending U.S. patent application Ser. No. 446,066 filed Feb. 26, 1974, now U.S. Pat. No. 3,907,477 issued Sept. 23, 1975 in the name of T. R. Jarboe et al discloses and claims a method and apparatus for fabricating laser-fusion targets, while articles entitled "Hydrogen Pellet Generation for Fusion Research" by C. D. Hendricks, "Production of Solid Pellets for Laser Initiated Target Plasma in BBII" by A. L. Hunt et al, and "Hollow Hydrogen Shells for Laser-Fusion Targets" by C. D. Hendricks et al, published in the Bulletin of the American Physical Society, Series II, Vol. 19, October 1974, pages 915, 963 and 927, respectively, are directed to fabrication of laser-fusion targets.
The success of any laser fusion system for the production of useful power depends critically on the production of suitable targets or fuel capsules which must satisfy a number of requirements in addition to low fabrication cost. Of critical importance to achieving sufficiently high energy gain are the effects of plasma instabilities, fluid instabilities, and the symmetry of the implosion. Thus, the target must have characteristics such as material composition, structure, and surface finish which are tailored to the laser pulse length, energy, peak and average power, and pulse shape.
The initial phase of a laser-driven implosion is the formation of an atmosphere surrounding the target, and thus efforts have been directed to various target configurations which are capable of producing this atmosphere, as well as other means such as gas injection, ablating of the explosive-chamber wall surface, etc. which produce a desired atmosphere about the target or fuel capsule.